How does increasing oil production from unconventional reservoirs using hydraulic fracturing and horizontal drilling affect the water budget of an oil field? Here we evaluate the evolving water issues in the Permian Basin with increasing production from unconventional reservoirs and potential synergies in terms of water management. We compare water used for and produced with oil and gas from conventional and unconventional reservoirs using a detailed well by well analysis of ~78,000 wells.
Water use is dominated by hydraulic fracturing, with increasing water use per well by a factor of ~10 and per foot of lateral by a factor of ~7 over the past decade. Produced water is generated primarily by conventional wells, averaging ~13 barrels (bbl) of water/bbl of oil, relative to ~3 bbl water/bbl of oil from unconventional wells (2005 – 2015). However, the large volumes of produced water from conventional wells are readily accommodated by injection into pressure-depleted reservoirs (water flooding) whereas produced water from unconventional wells cannot be directly injected back into the low permeability reservoirs but is injected into non-producing horizons, resulting in over-pressuring in some shallow zones and could induce seismicity. Joint management of water from conventional and unconventional wells and reuse of produced water for hydraulic fracturing may help resolve some of the water issues, such as water scarcity for hydraulic fracturing and over-pressuring from disposal of produced water.